Method for charging materials into blast furnace

ABSTRACT

The charging positions of iron bearing materials and a solid reducing agent to be charged into a blast furnace are adjusted by using a variable charging means such as an armor plate so that iron bearing materials and solid reducing materials alternately accumulate in the vertical direction of the furnace in layers which have coaxial circular vertices. The ore-coke ratio in the charged and accumulated beds of material in the furnace is substantially uniform in the radial direction of the furnace, resulting in a uniform upward gas flow rate at any section in the furnace. Thus, stabilized furnace operation and maximum furnace performance are achieved by improved gas utilization and the smooth entry of the falling charge material to the furnace.

United States Patent r191 lnaba et al.

[451 May21, 1974 METHOD FOR CHARGING MATERIALS INTO BLAST FURNACE [75] Inventors: Shin-lchi lnaba; Ken-Ichi Okimoto, both of Kobe City; Setsuo Tamura, Nishinomiya; Tashiyuki Uenaka, Kobe City, all of Japan [73] Assignee: Kobe Steel, Ltd., Fukiai-ku, Kobe,

Japan i [22] Filed: Sept. 7, 1972 21 Appl. No.: 286,886

[30] Foreign Application Priority Data Marv 6, 1972 Japan 47-22896 52 us. Cl. .Q 75/42 [51] Int. Cl .Q C21b 5/00 [58] Field of Search 75/41, 42

[56] References Cited v UNITED STATES PATENTS 2,516,190 7/1950 Dougherty et a1. 75/41 2,671,017 3/1954 McCutcheon 75/42 2,810,634 10/1957 Tofft 75/41 Primary Examiner-L. Dewayne Rutledge Assistant ExaminerM. J. Andrews Attorney, Agent, or Firm--Oblon, Fisher, Spivak, Mc-

Clelland & Maier [5 7] ABSTRACT The charging positions of iron bearing materials and a solid reducing agent to be charged into a blast furnace are adjusted by using a variable charging means such asan armor plate so thatironbearing materials and solid reducing materialsalternately accumulate in the vertical direction of the furnace in layers which have coaxial circular vertices. The ore-coke ratio in the charged and accumulated beds of material in the furnace is substantially uniform in the radial direction of the furnace, resulting in a uniform upward gas flow rate at any section in the furnace. Thus, stabilized furnace operation and maximum furnace performance are achieved by improved gas utilization and the smooth entry of the falling charge material to the furnace.

2 Claims, 15 Drawing Figures PATENTED M Mill? FIG. 1

. ATENTEB MY 2 1 i974 sum war 7 c w \\FURNACE CORE FURNACE WALL FIG. 6

PATENTEBIAY 2 1 m4 SHEEI 5 BF 7 FURNACE HALL/ PERMIABILI TY INDEX K ((65 UNI T5) FIG. 7

- FURNACE CORE/ SINTER TEMPERATURE C) PATENTEDHAY 2T 1974 T 3, 81 1,8 68

sums of 7 SINTER 8 C I6,S]-"I,C2-'b,52-'8 Lu a s 0 l l l I FURNACE/w FURNACE CORE WALL WALL-SIDEOF CORE-SIDE OF THE MIDDLE PART THE MIDDLE PART 800T- R0. I 600- ao- 3Q; 0 g I R00- SLEgzo- V Z I r 8 3 TEMPERATURE w A c \FURNACE WALL T y FURNACE CORE/- MTENTED MAY 21 197 SHKU 7 0F 7 O O M 5 EQQSEE W W SINTER FIG. 15

CHARGING PERIODACTORDING TO THE PRBENTWVENTTON CHARGING PERIOD ACCORD- ING -TO PRIOR ART METHOD $.5 EE mi METHOD FOR CHARGING MATERIALS INTO BLAST FURNACE t BACKGROUND OF THE INVENTION 1. Field of the Invention:

This invention relates to a method of charging iron ore or iron bearing materials such as iron ore pellets, sintered ores, etc., and a solid reducing material such as coke to a furnace byway of a variable charging means such as an armor plate or collision plate located in an upperregion of the blast furnace so that the ore coke ratio in the stock will be substantially uniform in the radial direction of the furnace.

2. Description of the Prior Art:

Various methods have been proposed concerning the charging of stock materials into a blast furnace. However, none of these methods have been proved to be satisfactory in practical operations. A principal disadvantage of these methods has been that it is almost impossible to attain a uniform ore-coke ratio in the charged and accumulated stock in the radial direction of the furnaceQThis would often result in a radially biased distribution of the gas flow in the furnace, slipping of the charged materials and even damage to the t'uyeres and/or cooling means in the furnace. Thus, it is difficult to maintain a continuous, stable furnace operation. Particularly in a large-sized blast furnace, the behavior'of the charged materials associated with the accumulation of the materials and the mixing or entry of these materials is'complicated. With some types of materials, fluctuations occur'in the behavior of the materials. making it still more difficult to obtain a uniform distribution of the ore-coke ratio of the stock in the radial direction of the furnace.

Attempts have been made to overcome these problems by carefully selectingthe optimum values of the coke base (amount of coke charged in one charging cycle) in the charge or of the stock level (height of the stock in the shaft) so as to obtain as good a material distribution as possible. However, it is almost impossible to vary these factors frequently enough to adjust to the variations in the condition of the furnace. In the past, blast furnaces have been provided with a movable charging means (such-as a repulsionplate) in the upper regions of the furnaces to achieve auniform ore-coke ratio ofthe charge materials. However, this type of furnace is rarely used becauseit does not operate satisfactorily and because of other problems such as maintenance. Otherdisadvantages occur because the positions of the charging means are always secured, and set positions of the charging means must be determined in order to charge iron oreand the solidreducing material (coke) to the furnace. Therefore, each material' charged to the furnacetends to concentrate in a certain specified area of the furnace, resulting in radially biased accumulation of material.

SUMMARY or THE lNVENTlON Accordingly, it-is anobject of the present invention to provide an improved method for charging stock materials into a furnace which is free of the above-said conventional defects, whereby rows of material can be chargedinto a furnace to achieve an optimum distribution pattern of :the materialsforthe most'effective blast furnace operation. That is, the gas flow in the-furnace is rendered substantially uniform in any section of the 2 furnace in order to improve the gas utilization efficiency (efficiency in the utilization of CO gas for the reduction of iron oxides and for heat exchange). Also, an ideal stock accumulation pattern can be produced which allows smooth entry of the falling charge material in the furnace.

Another object of the present invention is to provide a method for charging stock material into a blast furnace whereby the ore-coke ratio in the radial direction is rendered substantially uniform by controlling the charging positions such that the circular vertices of both layers of the solid reducing materials are located in the radial direction of the furnace between the circular vertex of one layer of an iron bearing material and the circular vertex of a second layer of iron bearing materials. This results in a stabilized and highly efficient blast furnace operation.

Briefly, these and other objects of the present invention are achieved by alternately charging'a solid reducing material and an iron bearing material to a blast furnace by way of a variable charging means to form layers of material having coaxial circular vertices. The charging process comprises: I

l. a first step consisting of the charging of a solid reducing 'material C, followed by the backward charging of an iron bearing material 0 and,

2. a second step consisting of the charging of a solid reducing material C followed by the forward charging of an iron bearing material 0 Both circular vertices of'the layers of the solid reducing materials C. and C are located in the radial direction of the furnace between the circular vertex of the iron bearing material 0 and the circularvertex of the iron bearing material 0 According to a more specific embodiment of the present invention, the vertex positions in the two accumulated layers of an iron material and a solid reducing material are formed in one cycle of a charging operation, wherein each cycle comprises the following two steps:

1. The first step consists of charging a solid reducing material C, followed by the backward charging of an iron bearing material 0 The vertex of the 0, layer is located closer to the furnace core or wall than the vertex of the layer of said solid reducing I material C, already added to the furnace;

2. The second step consists of charging a solid reducing material C followed by the forward charging of an iron bearing material 0 The vertex of the O layer is located closer to the furnace wall, if 0, is located next to the core, than the vertices of the layers of said solid reducing materials C, and C already added to the furnace. The vertex of layer r 0 is located closerto the core, if 0 is located next to the furnace wall, than the vertices of the layers of said reducing materials.

BRIEF DESCRIPTION. OF THE DRAWINGS The present invention will be more clearly understood by reviewing the following detailed description of the preferred embodiments of the invention when takenin conjunction with the accompanying drawings, in which:

FIG. 1 is a partial, vertical, sectional view of a model blast furnace;

FIGS. 2A, 2B and 2C are schematic illustrations showing the sequential mode of entry of the falling charge material and the mode of accumulation of the pellets of iron bearing material in the furnace;

FIG. 2 is a schematic illustration showing the mode of entry of the falling charge material and the mode of accumulation of the sintered grains of iron bearing material in the furnace;

FIGS. 4 and 5 are graphs showing the radial ore/coke distribution patterns in the furnace as observed when the charging position of the coke in the model blast furnace is fixed while the pellet and sintered grain charging positions are varied;

FIG. 6 is a series of graphs showing the radial ore/- coke distribution patterns in the furnace as observed when the pellet and sintered grain charging positions are fixed while the coke charging position is varied;

FIG. 7 is a diagram which shows the manner of entry of the falling material and the accumulation of material as the materials are charged according to the method of the present invention;

FIG. 8 is two graphs showing the ore/coke distribution patterns-obtained when the materials are charged as pellets or sintered grains according to the present method;

FIGS. 9 and 10 are graphs showing the variation of the permeability index in the radial direction of the furnace as observed when the materials are charged according to a conventional method and according to the present method, respectively;

FIGS. 11 and 12 are graphs showing gas compositions and temperature profiles in the radial direction in the stock in an upper region of the furnace as observed in actual operations, respectively, of a conventional method and of the present method; and,

FIG. 13 is a series of graphs showing the fuel ratio and the number of times of slipping in the actual operations of a conventional method and of the present method, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Numerous experiments and test operations were conducted until the limitations of the present invention were reached. Particular attention was concentrated on the mode of entry of the falling materials and the mode of accumulation of the materials as they were charged into the furnace, as well as the patterns of concomitant distribution of the gas fiow in the furnace. The following description of the invention is presented, and will center around the results of the experiments and test operations.

Pellets and sintered grains (sintered ore) were mainly used as iron bearing materials in the experiments. These materials lately, have become of major interest in the metallurgical industries. Coke was used as the solid reducing material in the process of this invention. A movable armor plate coaxially disposed with the furnace core in an upper region in the interior of the furnace was employed as a means for controlling the distribution of the charge materials. The experiments and test operations were conducted under two conditions. In the first test, a model reduced in size to l/ 10 the actual blast furnace size was used, while in the second test, an actual. large-sized blast furnace was used.

The first portion of the discussion will focus on the method as conducted in a model furnace, while pointing out the salient experimental results with reference to the drawings.

The model test apparatus (model blast furnace) used was of a half-cylindrical structure which was an actual replica of a blast furnace of the portion from the middle of the shaft to the large bell on a l/lO reduced scale. The structure was made from a' transparent resin plate so that an unobstructed view of the interior of the furnace was possible from the outside. FIG. 1 shows a vertical section of a portion of this apparatus, comprising a large bell (1), a hopper (2) and an armor plate (3) which is freely movable in a lateral direction to the furnace wall (4) and to the furnace core (5) within the distance between points (A) and (B), and which is coaxially disposed with respect to the furnace core (5). In the experiments conducted with this model furnace, the distance (A to B) through which the bottom end of the armor plate (3) is radially movable was divided equally into 10 sections. The mode of entry of the falling materials and the mode of accumulation of the materials charged into the furnace were observed by changing the position of said plate between the 10 sections. The radial distribution patterns of the iron bearing materials and coke in the furnace were determined by sampling each' of said materials by a tubular sampling device (not shown), and then analyzing them. The grain sizes of the charged materials used in this portion of the experiments were about l/5 of those used in a real blast furnace. Thus, the pellets used in the experiments possessed a grain size from I to 5 mm. The sintered grain sizes ranged from 3 to 10 mm. The coke particle sizes ranged from 5 to 15 mm. 4

Generally, the distribution patterns exhibited by the various kinds of accumulated materials in the upper portion of the blast furnace assumed an M shape, a V shape or some other similar shape depending on the sectional configuration of the stock line. In any case, the pellets demonstrated a peculiar behavior, as described below, when charged into the furnace. As shown in FIG. 2, the pellet charge (7) which has fallen on the coke layer (6) is biased toward the furnace wall (4). As the falling particles impinge upon the surface of the accumulated materials, they quickly spill over the crest and force the upper portion of the coke layer down the slope toward the furnace core (5) (see FIG. 2A). The force of theflow of particles causes the coke in the central area (the area halfway between the furnace wall and the core) to flow toward the furnace core and form a shelf (8) of coke in the central area closer to the furnace core. This shelf terminates as a mixed layer composed mainly of coke having a long slope which prevents a succeeding charge of pellets from flowing toward the furnace core (see FIG. 2B). As the falling pellets increase the size of the vertex, the slope of the pellet layer (7) is gradually increased. As a critical angle is reached, an avalanche of particles flows down from the vertex towards the core of the furnace. At the same time, the shelf, which had been restraining the avalanche of the pellet mass toward the furnace core, is swallowed up in the avalanche of pellets, and a perfect pellet-coke mixture layer (9) is formed near the furnace core (see FIG. 2C).

As described above, the shelf (8) has alarg'e slope which is built up at a middle point and is biased toward the furnace core. This shelf is engulfed in the pellet flow and is forced with said pellet flow toward the furnace core, so that the ore-coke ratio in the stock near the furnace core (5) is lowered. The ore-coke ratio, however, is relatively increased in the region of the shelf as a result of the damming of the pellets by the shelf. This phenomenon occurs no matter at what position and at what angle the armor plate is set. It also occurs when no armor plate is used.

The following description applies to the situation when sintered grains are used. As shown in FIG. 3, when the sintered grains impinge upon the coke layer (6), they do not quickly spill over the crest of the vertex as the pellets do because the sintered grains are a spongy-mass and their shapes are deformable. Also, since the sintered grains are closely analogous in shape to the coke particles, they tend to grip each other. Hence, no large coke shelf, as in the case of pellets, is formed. However, a coke-sinter mixture layer (9) is formed near the furnace core portion, and since the sintered grain accumulation line is relatively close to a straight line as compared to the .ore pellet case where the coke accumulation curve possesses a concave configuration between the central region of the furnace and the furnace core and describes a large circular arc, the ore-coke ratio is also increased in the central region close to the furnace core as in the case of the ore pellets. Also, since the sinter mass is spongy and deformable, the ore-coke ratio may be excessively increased in the neighborhood of the furnace wall, depending upon the position of the armor plate.

Thus, whether sintered grains or pellets are used, an ore-coke mixture layer is created near the furnace core area which has a decreased ore-coke ratio. Asa consequence, the gas flow rate increases near the furnace core, resulting in a non-uniform gas flow distribution in the furnace and an increased tendency of the charges to descend in the area near the furnace core.

FIG. 4 shows the ore/coke distribution patterns in the radial direction in the furnace as witnessed when the coke and pellets are charged alternately by fixing the position of the armor plate relative to the coke while varying the position of said plate relative to the pellets. FIG. 5 shows the patterns obtained when sintered grains are used. The figures labeled with the letters P and S indicate the armor plate positions set for the charging of pellets and sintered grains, respectively. As the number adjacent the letter Por S in the figure is increased, the amount of material charged toward the furnace core correspondingly increases.

As is apparent from these graphs, the ore-coke ratio is reduced near the furnace core both in the instances where pellets or sintered grains are used for the aforesaid reasons. It has also been noticed that even if an optimum position of the armor plate is set for charging the pellets or sintered grains, a non-uniform ore/coke accumulation distribution is produced while charging the coke particles and said iron-materials if the position of the armor plate is not maintained in its position throughout the operation.

FIG. 6 shows the ore/coke distribution patterns ob served when the position of the armor plate set for the pellets and sintered grains is fixed while varying its position for the charged coke. These graphs show that changing the position of the armor plate when coke is charged to the furnace exerts a greater influence on the distribution patterns of the materials than when the po sition of the plate is charged for the charging of pellets or sintered grains as shown in FIGS. 4 and 5.

Thegraphsin FIGS. 4 to 6 indicate that in order to obtain an optimum operation from a uniform ore/coke distribution in the blast furnace, the charging position of the solid reducing material (coke) should not be widely separated from the charging position of the pellet or sintered grain iron bearing material. The graphs also indicate that optimum performance is more sensitive to the charging position of the iron bearing materials than the solid reducing material. Thus, more care must be exercised in controlling the addition of the iron bearing materials.

In view of the results obtained in the present invention, the conventional charging method, in which the materials are repetitively charged through fixed charging positions of both the solid reducing material and the iron bearing material (one charging cycle of this method will be expressed hereinafter as a 'C l O 1 pattern), has been obviated. Instead, a new charging method is employed in which the iron bearing material charging position is not fixed relative to that of solid reducing material, but is varied between two locations so that the iron bearing material is alternately charged from these two locations (one charging cycle of this new method is expressed as a C iO lC 1O 1 pattern). Further, in order to obtain optimum accumulation of the materials (uniformore/coke distribution), the iron bearing materials 0 and 0 are accumulated in the furnace in such a manner that the vertices of the layers will be located more closely either to the core side of the furnace and then the wall side of the furnace, or to the wall side of the furnace and then the core side of the furnace, than the vertices of the layers of solid reducing materials C and C which have accumulated in the furnace. There is no established positional relationship between the vertices of the C and C layers. However, there is an indispensable positional relationship between the iron bearing material 0 1 and 0 layers. It is necessary that the vertices of the iron bearing material 0 and 0 layers be located more closely to the furnace wall or core with the vertices of the solid reducing materials C and C layers located between the vertices of the iron bearing material layers in the radial direction of the furnace.

It should be understood from the discussion that in the method of this invention, one charging cycle can be resolved into two steps.

The modes of entry of the falling material and the accumulation of the materials charged according to the method of this invention (c,lo,1c,to,t are shown in FIG. 7. The armor plate is first set at the charging position to charge the solid reducing material C, to form a firs circular vertex having a given radius. Next, the plate is set at 0 that iron material 0 will be charged biased towar the furnace wall (4) relative to C, to form a second circular vertex having a radius greater than said given radius, and then set atg pso that the solid reducing material C will be charge more closely toward the furnace core (5) than 0, to form a third circular vertex having a radius less than the radius of aid second circular vertex. Finally, the plate is set at :0 that iron material 0 will be charged biased towar the furnace core (5) relative to C and C to form a fourth circular vertex having a radius less than said first and third circular vertices.

The ore/coke distribution patterns obtained according to the method of the present invention as practiced in a model blast fumaceare shown in FIG. 8. Here, however, the armor plate positions for coke charging was set and secured at C C and one charging cycle using iron pellets had the pattern capl cnm and an- It has also been confirmed from surveys of the charged layers that the gas permeability which directly influences the gas flow in the blast furnace can also be rendered uniform in the radial direction by employing the charging cycle of the present invention. The results of the surveys are shown in terms of the permeability index in FIGS. 9 and 10. FIG. 9 shows the permeability index variation patterns demonstrated by a conventional ClO lcharging method where the pellet and sintered grain charging positions are set on the furnace core side and on the furnace wall side with respect to the coke charging position. FIG. shows the penneability index variations obtained by the method of the present invention in which charging of the furnace was conducted by combining the respective CiOlcharging patterns of iron pellets and sintered grains in a cyclic charging pattern of: C,1O,1C 1O 1(C,1P,1C lP tor C, ts lC lst). The permeability index (L) is determined by the pressure loss (AP) in the bed. L represents the height of the bed, p. the gas viscosity, p the gas density and e the superficial velocity in the Column X. The results of the measurements revealed the existence of the following relationship: K AP/(L'# p- 'e In a comparison of FIGS. 9 and 10, it can be readily noticed that the charging method of the present invention is superior to the conventional methods with respect to the permeability index.

As viewed above, according to the method of the present invention, the ore/coke distribution in the furnace as well as the permeability index is rendered highly uniform. This allows a more uniform and more effective utilization of the gas flow in the furnace for treatment of the charged materials.

So far, the invention has been described centering around the mode of entry of the falling material and the mode of accumulation of the charged materials in the radial direction of the furnace and the concomitant gas flow distribution pattern, based on the experimental results obtained by practicing the invention in a model laboratory apparatus. Now, the actual performance of the present invention as used in a full scale blast furnace is described in comparison with the prior art methods.

The furnace used in the tests was a large-sized blast furnace having an interior capacity of 2,843 m Charging tests were conducted by using to 75 mm-size coke particles as the solid reducing material, and 5 to mm-size pellets as the iron bearing material. The furnace was provided with a movable armor plate in an upper part of the shaft, a sampling device for determining gas compositions (C0, C02), and a means for determining the temperature distributions in the charged material layers in the upper regions of the furnace. The positions of the armor plate were determined in the same manner as in the case of the model furnace by dividing the radially movable range in the furnace equally into 10 sections. The position closest to the furnace wall side was designated as the 0 position and the position closest to the core side was designated as the l 0 position.

In FIG. 11 are shown the gas compositions and the temperature distributions in the stock in the upper region of the furnace as observed when a repeating C i0 1(C1Pl) charge pattern was employedaccording to a conventional method. Charging of the materials was conducted by setting the armor plate at position 6 (C 6) for the coke and at position 4 (P 4) for addition of the iron containing pellets. FIG. 12 shows the gas compositions and temperature distributions obtained when a 0, 0, 0,10, catamaran charge pattern was employed according to the method of the present invention. The armor plate positions were at 6 for coke (C C and at 3 and 7 for pellets P. and P respectively.

Both figures indicate that in the case of the C lPl charging cycle, the CO concentration (percent) and temperature are abnormally high, while the CO concentration (percent) by contrast is low in the portion of the layer near the furnace core, suggesting that the gas flow of the shaft is greater than the flow in the layer portion near the furnace core. In this example, the temperature in the layer portion near the furnace core often exceeds l,000 C. On the other hand, in the case of a C 11 (C 1 cycle pattern according to the present invention, the gas flow in the portion near the furnace core decreases while the gas flow near the furnace wall is promoted, thus producing a uniform gas distribution overall. The same situation is observed with the temperature distribution. No abnormally high temperatures are produced in the area close to the furnace core as is often observed in conventional methods.

This full scale operation was conducted for a period of 3 weeks, while periodically surveying the fuel ratio (the total amount of consumption of coke and heavy oil) and the slipping phenomenon. The results are shown comparatively in FIG. 13. It is apparent that, according to the method of the present invention, both the fuel ratio and the number of times of slipping are markedly decreased as compared to prior art methods. This attests to the fact that, in the present invention, the descent of the accumulated materials in the furnace proceeds in a most satisfactory form, the gas flow in any section of the furnace is uniform, and the reduction of iron oxides by CO is conducted at an extremely high efficiency.

As described above, the ore/coke ratio in the stock material in the furnace is confined within a small range rendering the gas flow and temperature distributions uniform. Also, the reduction of the iron oxides in the furnace is expedited (causing a decline in the fuel ratio), allowing a smooth drop of the furnace charge and stabilized furnace conditions. This results in a minimum of slipping and a minimum of damage to the tuyeres and other elements in the furnace. Thus, an extremely efficient and economical blast furnace operation is realized.

In the above-described experimental procedures and practical operations, pellets and sintered grains were used as the iron raw materials, but it was found that many other types of iron ores exhibit similar behavior. Their behavior is not as striking as the behavior of the pellets, but they can be used to accomplish the objectives of the present invention. Also, although in the embodiments shown, an armor plate was used as the material charging means, it is possible to use any other means provided that said means is Capable of charging the materials to the furnace core and its charging position is freely adjustable in the radial direction in the furnace.

While the present invention has been described by way of some preferred embodiments thereof, it will be apparent to those skilled in the art that the present invention is not restricted to the particular embodiments shown hereinabove, but various changes and modifications in the details of its arrangement and process can be made without departing from the scope of the invention.

Accordingly, what is claimed as new and intended to be covered by letters patent is:

1. A method for charging materials into a blast furnace having a variable charging means for alternately charging solid reducing materials and iron bearing materials to form layers having coaxial circular vertices which comprises: I

l. a first step consisting of the charging of a solid reducing material (C to form a first circular vertex having a given radius followed by charging of an iron bearing material (0,) to form a second circular vertex having a radius greater than said given radius and,

2. a second step consisting of the charging of a solid reducing material (C to form a third circular vertex having a radius less than the radius of said second circular vertex followed by charging of an iron bearing material (O to form a fourth circular vertex having a radius less than said first and third circular vertices,

wherein the circular vertices of both layers of the solid reducing materials (C and (C are located in the radial direction of the furnace between the circular vertices of the layers of iron bearing materials (O and (O 2. The method of claim 1, in which the iron bearing materials are used as pellets or sintered grains and coke is used as the solid reducing material. 

2. a second step consisting of the charging of a solid reducing material (C2) to form a third circular vertex having a radius less than the radius of said second circular vertex followed by charging of an iron bearing material (O2) to form a fourth circular vertex having a radius less than said first and third circular vertices, wherein the circular vertices of both layers of the solid reducing materials (C1) and (C2) are located in the radial direction of the furnace between the circular vertices of the layers of iron bearing materials (O1) and (O2).
 2. The method of claim 1, in which the iron bearing materials are used as pellets or sinterEd grains and coke is used as the solid reducing material. 